The music industrial complex accepts the second hand CD market because they have to because of the
First-sale doctrine. You don't get first-sale rights with a digital download from iTunes, Amazon or wherever because
those rights get licensed away in the sale agreement.
One of the reasons I buy CDs (usually used) is because I own them to the extent that I can resell them, trade them, give them away as gifts, whatever. CDs also give me a lossless copy of the music. I don't get that with digital downloads, even the high res lossless digital downloads.
I
'm not excited about a future where all music is digital downloads and CDs and other physical media no longer exists. Good-bye used market. So long first-sale. A future with no used music market is not a future that I want. That's a future that will drive people to piracy just to get the music. Buy new at full price or don't buy at all and pirate, or make do with subscription services where your music collection goes away when the subscription runs out.
I'm not making any implications that the used CD market justifies piracy in any way because the artist doesn't get additional money in either case. I'm just saying that the artist doesn't gain much from the used market other than the original sale. That original sale is better than they get from piracy.